The Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) mixed ionic electronic conductor (MIEC) is considered to be one of the most promising perovskite-based materials for oxygen transport exhibiting high oxygen permeability. Such oxygen-permeable perovskite membrane maybe applied to increase efficiency of combustion or reforming processes of new fuels such as green ammonia. An approach to elevate the oxygen permeability of BSCF membranes is reduction of membrane thickness, as the permeation process is mostly controlled by bulk diffusion. Since self-standing thin membranes are not sufficiently mechanically stable, asymmetric membranes consisting of a thin layer membrane deposited onto a porous bulk support are usually employed. . In this work, planar BSCF thin film membranes of 1 to 2 and 15 to 20 µm thickness were successfully synthesized by a combination of magnetron sputtering (MS) and thermal annealing (TA) and/or selective laser annealing (SLA) processes. Thin films appeared to be pinhole-free with a high crystallinity of a single perovskite phase and a microstructure that showed suitability for oxygen permeation applications. Correlations between thin film properties and MS process parameters (e.g. power, Ar/O₂ ratio, pressure, etc.) and TA&/SLA parameters were established and optimised as key factors for producing thin film membrane exhibiting high oxygen flux and good stability. A variation of the oxygen flux through the BSCF asymmetric membrane as well as the porous substrate is presented as a function of temperature and also oxygen partial pressures applied to both sides of the membrane allowing for calculation of permeability of the deposited thin film.